1. Field of the Invention
The present invention relates to a head moving device for moving a head with respect to a disk. Particularly, the invention is concerned with a head moving device having a reduced size of a drive section for driving a head.
2. Description of the Related Art
FIG. 5 is a plan view showing a conventional head moving device 30 and FIG. 6 is a sectional view taken on line 6--6 in FIG. 5.
In the head moving device 30 shown in FIG. 5, a guide shaft 28 is fixed to a chassis (not shown), and a fitting hole (a bearing portion) 26d of a moving member 26 is fitted on the guide shaft 28. The guide shaft 28 is disposed in the radial direction of a disk D and is movable in the same direction.
On the moving member 26 are mounted a head body 27a on a 0 side opposed to the lower surface of the disk D and a head body 27b on a 1 side opposed to the upper surface of the disk, the head body 27b being fixed to the tip of an arm such as a plate spring extending from a support portion 26a of on the moving member 26 toward the disk D.
An extending portion 26b is integral with the moving member 26, the extending portion 26 projecting in an L shape sideways from the moving member, as shown in FIG. 6.
A drive section 31 is disposed sideways of the moving member 26. Although in FIGS. 5 and 6 the drive section 31 is disposed on only one side of the moving member 26, a drive section similar to the drive section 31 is sometimes disposed also on the opposite side of the moving member 26.
In the drive section 31, a coil 22 is fixed into a recess 26c with use of an adhesive or the like. The recess is formed by both support portion 26a and extending portion 26b. A generally turned square U-shaped guide portion 24 is provided at the distal end of the extending portion 26b, and a recess 24a of the guide portion 24 is supported by a sub-guide shaft 29 so as to be slidable with respect to the sub-guide shaft, the sub-guide shaft 29 being provided on the chassis side in parallel with the guide shaft 28.
A yoke 21b is inserted into a coil center hole 22a formed inside the coil 22. Also above the coil 22 is disposed a yoke 21a. Both yokes 21a and 21b are fixed at both ends thereof with screws. A plate-like magnet 23 having approximately the same shape as the yoke 21a is attached to the yoke 21a.
In the head moving device 30 constructed as above, when the coil 22 is energized, a drive force acting in the radial direction of the disk D is generated in the moving member 26. The moving member 26 is prevented from rotating about the guide shaft 28 by sliding contact of the sub-guide shaft 29 with the recess 24a of the guide portion 24. As the moving member 26 moves, the head bodies 27a and 27b slide in the radial direction of the disk D while holding the disk therebetween.
However, the following problems have been encountered in the above conventional head moving device 30.
In the head moving device 30, if driving sections 31 are disposed on both sides of the moving member 26, the whole of the device becomes larger in size, but if a driving section 31 is disposed on only one side of the moving member 26, the entire device can be somewhat reduced in size, as shown in FIGS. 5 and 6. However, for stabilizing the balance of the moving member 26, it is required to use such an expensive component as the sub-guide shaft 29 and thus it is impossible to attain a further reduction of cost.
Besides, as shown in FIG. 6, the plate-like shape of the yokes 21a and 21b is wider in the same planar direction as the disk D, and the coil 22 is also wide planarly. Consequently, as shown in FIG. 5, the distance L2 between a work line of a driving force F generated in the coil 22 (a center line S1 in the width direction of the coil) and a center line S2 of the guide shaft 28 becomes very long, so that a planar moment M acting on the center of the moving member 26 during operation becomes very large. As a result, a sliding friction force between the fitting hole (bearing portion) 26d of the moving member 26 and the guide shaft 28 becomes large and the motion of the moving member 26 becomes stiff, or the guide shaft 28 and the fitting hole (bearing portion) 26c is apt to wear.